


Mer-aculous!

by mermanfromdownunder



Category: Miraculous Ladybug
Genre: Canon Universe, F/M, Mermaids, Mermen, Transformation, chat noir merman, h2o just add water - Freeform, ladybug mermaid, mermaid, merman
Language: English
Status: In-Progress
Published: 2018-05-10
Updated: 2019-05-01
Packaged: 2019-05-04 17:50:39
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 5
Words: 3,737
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14598447
Author URL: https://archiveofourown.org/users/mermanfromdownunder/pseuds/mermanfromdownunder
Summary: After the events of 'Syren' when Ladybug and Chat Noir are given the ability to transform into an aquatic form, the superhero duo discover a little problem....  [somewhat CANNON COMPLIANT]  -If you like it and want more leave a comment!-





	1. Prologue

**Author's Note:**

> Hopefully by now if you are into Miraculous Ladybug, you should have seen the episode 'Syren'. This story takes place exactly after the events of that episode, the prologue quickly recaps the important points of the episode if you haven't seen it, and sets up the premise for the story. I have 2 other Ladybug stories that I consider much better and thought out than this one currently, so if you like Ladybug I'd strongly suggest you check them out. Thanks and hope you enjoy the story.

~Prologue~

Once again, Ladybug and Chat Noir had saved Paris from one of Hawkmoth's akumatized villains. This one, Syren, was a teen girl called Ondine that Hawkmoth had transformed into a mermaid supervillain. She had been a formidable foe for the super duo, until Master Fu, with Marinette's help, had brewed up a special potion that granted Kwamis new powers and abilities to transform the Miraculous holder. 

Syren had flooded the streets of Paris with water, leaving Ladybug and Chat Noir almost completely useless. However the potion the Miraculous Guardian had concocted, granted the ability to transform into an aquatic form. Fins and the capacity to breath underwater gave the superhero duo the leg up they needed to swiftly defeat the villain and de-evilize the Akuma hiding inside. 

Adrien was glad to finally and properly meet Master Fu in person. After the ordeal, the Miraculous Guardian had visited his home incognito, posing as a replacement Chinese tutor. The man passed on the same wisdom and knowledge that he had told Marinette over the last few meetings to the eager blonde haired boy. He had also gifted Adrien the superpowered potion in the form of various coloured pieces of camembert, each colour representing a different ability. 

Meanwhile, the gang had rescheduled their 'Mecha Monkey vs. Cyber Shark 3' outing for the next showing that evening. Giving Marinette enough time to transform the Miraculous elixirs into a more practical form, mini macaroons, each also a different colour to indicate the different powers it will imbue the Kwami with. 

That night, Marinette felt strange all throughout the movie. Her skin felt dry and itchy, her throat parched and her legs ached. She had not had any popcorn, usually the salty snack would make her thirsty. She had ignored all of it the best she could while watching the film with her friends. Marinette had put it down to the very different to usual day she had, fighting a supervillain underwater. The water must have dried out her skin, all that swimming tired out her legs and she just needed a drink of water. 

Similarly, Adrien had felt off too. Ever since Master Fu had left, he continuously felt thirsty and had drunk 8 large glasses of water in only a few hours. Before bed, Adrien took a shower; while he usually took longer than the average boy, tonight he had been in the shower longer than he had ever before. The cool refreshing water cascading from his wet hair, down his face and over his body felt better than it ever had before. Plagg had gotten inpatient waiting for his evening cheese and almost dragged Adrien out of the shower with his whining. 

As Marinette walked home from the theatre, her legs still ached. She bought a bottle of water from the candy bar on her way out and had chugged it down as soon as possible, but she still felt dehydrated. Scratching at the skin on her neck, it felt flaky like one of her Dad's pastries, she quickly stopped herself when Tikki popped out of her purse to scold her. 

 

In the shower, Marinette reminisced her even more amazing than usual day of being a superheroine. Chat Noir and her were finally on the same page with Master Fu, she had gotten to try her new aquatic abilities and had made other power-up food for various occasions from Master Fu's translation of the mysterious grimoire. Before she knew it, her parents were knocking on the door asking if she was okay. She had been in there for over half an hour, but to her it had only felt like a few minutes. 

Both the exhausted superheroes climbed into their separate beds and went to sleep, ready to save Paris again tomorrow. Moonlight beaming through Marinette's skylight and Adrien's large window as the both dreamed about the day and each other.


	2. A Mer-mazing start to the day

It was a Saturday morning like any other for the protectors of Paris, that meant sleeping in. Without the burden of school the superheroes could relax in bed at least a couple hours longer than usual. But it seemed like their fight with Syren the day before had exhausted the pair more than usual. 

Marinette was still dead to the world when she got a text message from Ayla that woke her from her slumber. She groaned as she rolled over and checked her phone. 

[Wanna come to the park later? Word on the street is a certain someone is having another photoshoot there today.]

As soon as it clicked who the 'certain someone' was in the blue haired girls' head, she lit up like a Christmas tree. Scrambling to get out of bed and onto the floor, Marinette suddenly realised she still felt as terrible as she did last night. Beyond thirsty, legs in pain and incredibly itchy. She called for her magical Kwami, who zipped down and greeted her.

"Tikki, what's wrong with me, I feel like I have the flu or something." She spoke with a hoarse voice. 

"Hmmm. What is the matter exactly?" The Kwami asked. 

"My legs ache, I am really thirsty and I'm super itchy. Could it be something to do with the new transformations?"

"Master Fu might be the person to ask. Kwamis were never told much about the powered up transformations."

Marinette grabbed her clothes for the day and started heading to the shower. "Have any of the previous miraculous holders have these symptoms?"

"Not that I can recall. You should go see Master Fu today. This seems very strange and might be connected to what happened yesterday."

"I will Tikki, but Alya says Adrien is having a photoshoot in the park, I'll go see him after I'm done, I promise."

Tikki just made a slightly concerned face in reply as the girl went off to the bathroom. 

 

Adrien's alarm had been blaring for over a minute before Plagg finally shook Adrien awake.

"Ughha. Plagg, what is it?!" The awoken boy asked. 

"You need to get up, you have that thing today, but most importantly- I'm hungry!" The black Kwami yelped. 

"You truly are a cat, aren't you."

"And you are truly going to be late for your thing if you take as long in the shower this morning as you did last night."

Adrien opened his bedside draw and pulled out a container of camembert for his Kwami. This was met with great joy from Plagg, who even took a moment to saver the cheese before inhaling it like a videogame character. After lazily walking to the large ensuite bathroom, the boy took a moment to notice that he still felt off. 

"Nothing a nice shower can't fix." He said to himself as he stripped his stylish pajamas off and stepped into the shower. 

 

Marinette stepped into the spray of warm water and felt instant relief on her dried out skin and her aching legs. She even took a gulp of water straight for the stream to quench her insufferable need for water.

Adrien did the same; a waterfall of cool H2O cascaded over his shoulder and body, falling onto the tiled flooring and trickling down into the drain.

Suddenly, Marinette felt a sharp twinge in her legs and stumbled over into the wall as her legs fussed into one limb. She looked down in shock and noticed her legs had been replaced with a mermaids' tail. 

The boy closed his eyes to relish in the refreshing water. Instantly he felt a ferocious pain in his lower half and collapsed into the tiles. After wincing from the pain, he looked over at his feet, which had been metamorphosed into a fish tail. 

Both superheros shrieked in confusion and terror. Marinette's mermaid tail started at her hips, transitioning from skin to a pastel red scale pattern that covered the rest of her lower half and concluded at her feet to replaced by a semi-transparent fluke that looked like the flippers that she had in her Aquatic Ladybug form. Adrien's tail had a green and black tint to it depending on the different viewing angle. It finished at a neon green fluke that was similar to his aquatic form. 

"TIKKI!"  
"PLAGG!"

"HELP!"

**Notes for the Chapter:**

> Hopefully everyone is enjoying the story so far. If you did, please drop a comment or a kudos. If you didn't, maybe leave a constructive comment for me and I will do my best to fix it. If anyone has suggestions for further plot ideas, let me know.


	3. I'm a mermaid?!

"Marinette!" Tikki squeaked in surprise as she zipped into the bathroom, phasing through the wall. Water was still falling onto her, hitting her newly formed mermaid tail and making her blue hair sag with dampness.

\--------

Adrien called out again for his Kwami companion. Finally, Plagg nonchalantly appeared in the bathroom beside him. 

"Oh great, not this again." The small black sprite moaned.

"Again?!" Adrien spat. Moving out of the spray of water. He reached up and flicked the shower tap off with his outstretched fingertips before collapsing onto his stomach. 

"You need to go talk to Master Fu. Right after you get me some cheese."

"Urrhhrh. This is the worst day this could possibly happen. I've got the photoshoot Plagg! How do I make this, tail thing, go away?!"

\-------

"I'm a mermaid Tikki! What do I do!?" The blue haired girl asked in a flustered panic.

"I thought your symptoms sounded familiar. You have to get dry. You can't have any water touch your skin." Her Kwami responded.

"You mean, this has happened before?!" The girl reached for her towel and Tikki turned the taps off. 

"Yes, a long time ago. I had almost forgotten." 

"I'm going to go see Master Fu right now!" Marinette said, rubbing her towel along her tail, taking time to admire it's strange and beautiful nature. 

\--------  
"So you're saying I just need to get fully dry. And I'll be back to normal?" Adrien asked.

"That's it kid." Plagg answered, before shoving a slice of camembert into his void-like mouth. 

The blonde haired boy started to run the velvety towel over his body and tail. 

\-------

Both superheros were shocked when minutes later, once they were almost completely dry, a wave of coloured light made its way down their bodies and removed all evidence of their fish-like appendage, leaving them both naked on their respective bathroom floors. 

Adrien dressed in the attire set out for him by Natalie for the the photoshoot the night before. While Marinette got dressed in her usual pink jeggings and white floral shirt. 

Marinette shoveled her breakfast down as did Adrien, before leaving to their seperate tasks; Adrien to his photoshoot and Marinette to a hopefully quick visit to Master Fu. Both wished to know more about their weird transformation, and they both soon would.

**Notes for the Chapter:**

> Hope everyone is enjoying this so far. If you have any suggestions, leave a comment. And if you like it, leave a comment and a kudos. It encourages me to write more often! :)


	4. Fish out of water

"Ahhh, Marinette. Come for another lesson?" The Master asked, placing his tea cup down and standing from his chair as the young girl entered. 

Tikki rose out of Marinette's purse and floated next to the young girl. 

"I, think, I'm experiencing, side effects, from, the..." The girl stuttered. 

"Master Fu, Marinette turns into a mermaid when she gets wet!" Tikki finished for her. 

The old man stroked his beard. "Hmmm, very interesting. Would you please show me?" 

Marinette looked to Tikki who smiled with a look that instantly calmed her. Walking over to the side of the room, where Master Fu had been, sat an ornate tea kettle. She poured herself a cup of the lukewarm beverage before taking a deep breath and dunking her finger in the liquid. A few seconds later, the magical transformation wave turned her again into a tailed creature causing her to fall backwards. Swiftly for a man of his age, Master Fu caught the mermaid and layed her down on the tatami flooring.  
The pastel red scales shimmered in the diffused light coming through the translucent paper walls. Master Fu took a careful inspection of the newly transformed mermaid, touching her scales and running his fingers over the transition from skin to scale. Marinette had only just noticed that her top half was covered by a small area of scales that obscured her chest. She was thankful for the modesty since her clothes had magically disappeared. Her lips had gone glossy like her Aquatic form but her hair changed; instead of pigtails it was let out and flowed down onto her shoulders. 

"It seems to happen whenever I touch water." Marinette said meekly, laying her head back into the soft flooring. 

"And when she is dry she transforms back." Tikki interjected. 

Master Fu stroked his beard. "Yes, I see. This is very puzzling. In all my years of being a Miraculous Guardian, I've never seen this happen to anyone. Heard myths and stories, but I did not believe them." 

"Is there anything we can do about it? I can't do anything around water anymore. What if this happens when I'm Ladybug as well?" The girl cried.

"Have you tested that?" The master asked. 

"No, it's only just happened this morning, I came straight here." Marinette said with a frown, thinking about how this may effect both her civilian life and double life as a Parisian superhero. 

Master Fu tossed a towel to her. " You get dry and l'll get the spellbook and see if it says anything about this."

\------

"Smile Adrien, big smile! Like you've just seen the girl of your dreams!" The over-enthusiastic Italian photographer yelled across the distance between him and his subject. 

Normally when Vincent would say things like that, Adrien would start thinking of Ladybug and the adventures that she and him have, giving off the smile that Vincent was after almost instantly. But today was different. He was too preoccupied thinking about the tail thing. The gushing water fountain only a meter behind him didn't help the matter. But he played along as best he could, like he always did after a long night of patrolling, a particularly taxing Akuma attack, or when his friends were meeting up for something and he was stuck modelling.

\--------

Once Marinette had dried herself off, her legs, pigtails and clothing reappeared again with the transformation wave of light. Master Fu had looked up from the spell book for a second to see the metamorphosis before returning his gaze to translating pages.

"Any luck?" The girl asked, standing and walking over to the old man. 

"Not yet I'm afraid." He said, flicking a page. 

The small red sprite whizzed over from talking to Master Fu's kwami. "Marinette, why don't you transform to see if it affects Ladybug?" 

Marinette was hesitant, but she had to do it. "Tikki! Spots On!"

With a glow of magical light, the young girl changed into the normal looking red suited superheroine. 

"Okay, let's give this a try." Ladybug said to herself more than anyone as she stuck her gloved finger into the same cup of now cold tea. 

After a moment, the magical transformation happened again and she went from regular Ladybug to an interestingly weird version of the Aquatic form. 

The purple fins on the top of her hips that made up a belt with the help of a Ladybug buckle was now the transition point from skin to suit/scale. Her normally seperate lower limbs were now combined into one again, the textured suit replaced with fish scales ending with a similar fluke to before, with all the red colours feeling more vibrant and less pastel. The top half of her usual patterned suit was replaced with again an area of scales covering her chest, matching the changes in her tail. This left her untanned skin exposed apart from some small areas of scale on the outside of her forearms, where long and thin fins protruded. Her hair and hair accessories were the same as in her Aquatic form and her lips were just as glossy as before. 

Luckily for Marinette her mask had remained, the same as her Aqua form, but she still wasn't happy at how much of her suit had disappeared. But she had little time to take in the change before she lost her balance and fell onto the soft flooring face first. 

"Master Fu, you said you saw Chat Noir yesterday to give him the power up potions. Could he be experiencing something like this too, or is it just a, me thing." The mermaid said, twisting her torso around to look at the reading man. 

Putting the book down on the ancient table, the miraculous guardian walked over to inspect her new form. "Most likely he is going through the same thing but may not even realise it. You found out when you had a shower this morning, what if he skips his and finds out somewhere else. Possibly in civilian form."

Marinette's annoyed look turned to concern, for her partner, ally and friend. What if indeed he was out there unaware in civilian form and got wet, suddenly changing into a Chat Noir themed merman. She reached for the towel on the ground nearby and began to dry herself. 

"I told Chat Noir that if he ever needed anything to come here, and ring the bell on my rooftop. As he hasn't done that yet, it's safe to assume that he doesn't know about the changes you have experienced or might not be undergoing those himself." The old man informed. 

In a flash of light, the mermaid on the floor disappeared, replaced by regular old Ladybug with seperated legs and a fully complete suit. With a flip, she stood before detransforming back into civilian form. 

"Marinette, if you see Chat Noir you must tell him and send him to me before something happens."

The girl nodded. "I will Master." Then ran to the exit.

"Try to stay dry!" The man called after her before he returned to studying the grimoire.

**Notes for the Chapter:**

> If you'd like learn more about my works, please drop me a line on Instagram (@mermanfromdownunder)


	5. Slipping Away

"Mmmm. Yes, perfect! Okay Adrien, now stand up and walk slowly around the fountain." Vincent said, using his free hand to gesture while continuing to look down the viewfinder of the camera.

The blond haired boy complied and began to trace the lip of the water feature with his shoes.

"Something wrong Adrien? Give us a smile huh?" The overzealous photographer asked.

Adrien quickly realised that he was probably looking more worried than a regular person would about falling in. Seeing as it would expose himself as a merman to the world, a fate almost as bad as having himself revealed as Chat Noir. But he smiled and did his best to look professional and not scared for his live. What would happen if water splashed on his skin or if he accidentally slipped and his foot went in? He did his best to concentrate on the modelling and not falling in, but every few seconds, thoughts like that popped into his head.

A red streak caught his eye from the rooftops across the park.

"Ladybug….." He whispered to himself. What if she was experiencing this weird tail situation too, and didn't know about it?  
"Aaaa, Vincent, could we take a break? I'm famished. Sorry!" Adrien as he was zipping away, leaving the photographer dumbfounded.

Vincent lowered his camera. "But we only just got started? Oh well, guess a snack wouldn't hurt after all."

Behind a pillar in the nearest Métro stop, Adrien opened his shirt, letting his cheese craving kwami float out.

"Plagg, we have to go and warn Ladybug not to touch water." The boy said with determination.

"Eh, she probably already knows. She was probably looking for you, to tell YOU that." The grumpy sprite argued.

"Plagg, Claws Out!" Adrien called, not giving he kwami the time to draw breath, and in a flash his model outfit was replaced with the slick black leather, golden bell, belt tail and leather cat ears that made up his superhero persona. He sprung out of the Métro stairway and pole vaulted up into the Parisian skyline on his metallic staff.

\--------

Ladybug firmly landed on a rooftop and retracted her yo-yo back into her hand. She scanned the horizon for trouble; just incase her more unusual than normal magical transformation was the work of an akumatized citizen under the control of Hawkmoth. She was also keeping her eyes peeled for a particular stray cat.

She slid the top of her yo-yo to the side, and using her communication application she tried contacting her partner, but with no response.

"Urrrh. Where is that cat when you need him? He could be in trouble and I have no idea where he-" The spotted superheroine started to cursed. Chat joined her on the rooftop in a uncommon, but still uniquely Chat way, falling straight into his companion, knocking them both onto the roof. Ladybug was mildly annoyed but was glad to see Chat.

"Chat, there's something-" "M'lady, has anything weird happen-" They both started, but soon stopped before rising to sit.

"You first." Chat insisted.

Ladybug nodded in thanks. "There is something going on with me today, something to do with the power up potion we used yesterday to defeat Syren."

"Don't tell me, you turn into a mermaid whenever you touch water? I was just coming to warn you about that." Chat exhaled.

"You too?"

"Well, not a gorgeous mermaiden like you obviously, but similar. Merman I guess."

"Chat, this is serious. It happens in both our civilian and superhero forms. I've just been with Master Fu trying to work out what has happened."

"Really? I haven't tried it as Chat Noir."

"Yes, you will look a bit different, similar to your aquatic form. We should get back to Master Fu, but I'm glad you are safe Chat. I wouldn't have wanted to have to deal with this without you.…"

"We are a team, m'lady. Even if we turn into half fish, half people sometimes. "

 

\--------

After the duo had landed on Master Fu's rooftop, Chat rang the small chimes attached to one of the pillars of his awning.

"You know Ladybug, I think I was more worried about you than I was about myself this morning." Chat said openly.

Ladybug blushed a little in response. "Really?"

"Of course."

She changed the topic, not wanting to admit her own worry about him. "Did you feel, weird last night by any chance?"

Chat thought for a moment. "All afternoon I was incredibly thirsty. And I spent waaayyy to long in the shower before bed."

"As did I, I felt parched all night." The spotted superheroine replied.

The trapdoor opened nearby and the Miraculous Guardian poked his head out. "Ah, Ladybug, Chat Noir. Please, come in." He beckoned the pair inside. "There is much to discuss now that you are both here."

**Author's Note:**

> If you have any suggestions, drop a comment. If you really like it, please leave a comment or a kudos and it helps me want to write more often. While you wait for the next chapters, why not check out my two other Ladybug stories or my many other mermaid fics! If you'd like learn more about my works, please drop me a line on Instagram (@mermanfromdownunder)


End file.
